A digital video signal may be processed to form a bit stream having a reduced bit rate. Such processing for bit rate reduction may be implemented according to an MPEG compression method, and may be formatted, for example, with an MPEG compatible structure, such as that employed in a digital satellite system, for example DSS™ or the proposed Grand Alliance or GA terrestrial system.
A consumer video recorder may be adapted to provide recording capabilities for both analog signals and digitally encoded signals processed for example, for compatibility with an MPEG standard and having GA or DSS™ signal formats. The adapted consumer video recorder may be considered as two electronic systems within one box, sharing a recording mechanism, servo and control systems. A conventional analog recording method may be employed where an analog luminance signal component frequency modulates an RF carrier and an analog chrominance signal component amplitude modulates a second RF carrier. When reproduced, the two modulated signals are demodulated, combined and coupled out for video display.
During both record and replay operating modes, on-screen display messages may indicate operational status, warning conditions, tape duration, record time, time code etc., of the video recorder. These on-screen display messages or OSDs may be added to the analog video output signal to provide the user with recorder status information.
Digital recording may be achieved by using the consumer video recorder as a digital bit stream recorder/reproducer. The MPEG compatible bit stream, for example transports packets, may be recorded by reformatting the transport packets to facilitate recording and reproduction. For example, the transport packets may be buffered and error detection and correction data words computed and added. The bit stream with error correction added may be formatted into recording data blocks or sync blocks containing a predetermined number of bytes which may be accommodated in each recorded track. The sync block signal may be coded to render the signal more suitable for digital recording, for example, to remove any DC component, or provide spectral shaping of the recorded signal, such modulation may be produced by “code book” type encoding. In a playback mode the recording processes are effectively reversed, for example, the “code book” encoding is decoded, errors are detected and corrected and the sync block formatting is removed restoring the bit stream to the original MPEG like format.
To minimize the additional cost increment of digital recording and reproduction, MPEG decoding and encoding is not included in the recorder. Thus the recorder must process the MPEG like packet stream without changes or additions. Hence the recorder provides a program delay or time shifting facility. However, recorder status and warnings and tape timer displays, which during analog operation are added to the analog output signal, may be absent during digital operating modes. Hence, recorder status, etc. may only be ascertained by observation of the recorder control panel.
System interconnection and control between a digital signal source, recorder and monitor display may be simplified by the use of a bi-directional data bus. However, any interconnection additional to that of an analog system may present the user with incomprehensible installation complexity and confusion. A simple interconnection method is required which may provide coupling between a digital signal source and display regardless of a recorder's operational status. The simple interconnection method must facilitate both analog and digital recorder operation by utilizing the same interconnection system. In addition, recorder status and warning messages are required for user display during both analog and digital recorder operating modes.